A steering system for detecting a hand wheel position is provided and includes an input shaft connected to a hand wheel, a main gear disposed around the input shaft, a puck gear meshingly engaged with the main gear, and a control module. The control module receives an angular main position of the main gear and an angular puck position of the puck gear. The control module includes a rotational calculation module for calculating the hand wheel position based on at least the angular main position and the angular puck position.
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1. A steering system for detecting a hand wheel position, comprising:
an input shaft connected to a hand wheel;
a main gear disposed around the input shaft;
a puck gear meshingly engaged with the main gear; and
a control module, implemented in a hardware processor, for:
receiving an angular main position of the main gear and an angular puck position of the puck gear;
setting an empirical value equal to c1- 1/g c2, wherein c1 is the angular main position, c2 is the angular puck position, an g is the gear ratio;
finding a number of rotations of the input a number of rotations of the puck gear using the empirical value;
calculating a first hand wheel position based on the number of rotations of the input shaft;
calculating a second hand wheel position based on the number of rotations of the puck gear; and
determining that the first hand wheel position is incorrect if a difference between the first hand wheel position and the second wheel position is above a threshold value.
9. A steering system for detecting a hand wheel position, comprising:
an input shaft connected to a hand wheel;
a main gear disposed around the input shaft;
a puck gear meshingly engaged with the main gear; and
a control module, implemented in a hardware processor, for:
receiving an angular main position of the main gear and an angular puck position of the puck gear;
setting an empirical value equal to c1- 1/g c2 wherein c1 is the angular main position, c2 is the angular puck position, α is the hand wheel position, an g is the gear ratio;
finding a number of rotations of the input shaft from a lookup table saved in a memory of the control module using the empirical value; and
calculating the hand wheel position based on the number of rotations of the input shaft,
wherein the hand wheel position is related to the angular main position and the angular puck position by: c1 =α- 360n 1, c2=G α- 360n2, and α=c1 +360n1, wherein α is the hand wheel position, n1 is the number of rotations of the input shaft, and n2 is a number of rotations of the puck gear.
2. The steering system as recited in
3. The steering system as recited in
4. The steering system as recited in
5. The steering system as recited in
6. The steering system as recited in
7. The steering system as recited in
8. The steering system as recited in
10. The steering system as recited in
11. The steering system as recited in
12. The steering system as recited in
13. The steering system as recited in
14. The steering system as recited in
α′=(c2 +360n2)/g wherein α′ is the second hand wheel position.
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This patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/579,770 filed Dec. 23, 2011 which is hereby incorporated herein by reference in its entirety.
The present invention relates to a steering system, and more particularly to a steering system for detecting a hand wheel position.
Some types of steering systems may require the detection of hand wheel position to provide safety features, or for certain types of algorithms. Several approaches currently exist for determining the hand wheel position. However, some of these approaches may not include the level of precision that is needed. For example, one type of hand wheel position detection system may require a five degree diagnostic limit Hand wheel position detection systems that are currently available may not be able to meet this requirement.
According to one aspect of the invention, a steering system for detecting a hand wheel position is provided. The steering system includes an input shaft connected to a hand wheel, a main gear disposed around the input shaft, a puck gear meshingly engaged with the main gear, and a control module. The control module receives an angular main position of the main gear and an angular puck position of the puck gear. The control module includes a rotational calculation module for calculating the hand wheel position based on at least the angular main position and the angular puck position.
According to another aspect of the invention, a steering system for detecting a hand wheel position is provided. The steering system includes an input shaft connected to a hand wheel, a main gear disposed around the input shaft, a puck gear meshingly engaged with the main gear, and a control module. The control module receives an angular main position of the main gear and an angular puck position of the puck gear. The control module includes a rotational calculation module for calculating the hand wheel position based on at least the angular main position and the angular puck position. The control module includes a diagnostic module for determining an error of the hand wheel position by comparing the hand wheel position with a second hand wheel position.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring now to
The ring magnet 26 is disposed around the input shaft 22 and is located within the main gear 24. The puck gear 30 includes a puck magnet (not shown) that is molded into the puck gear 30. In the exemplary embodiment as shown in
A plurality of first magnetic field sensors 50 are provided for detecting the position of the ring magnet 26 located within the main gear 24, and plurality of second magnetic field sensors 52 are provided for detecting the position of the puck gear 30 (the second magnetic field sensor 52 is shown in phantom line). The first and second magnetic field sensors 50 and 52 may be any type of sensor for detecting the angular position of the ring magnet 36 or the puck gear 30 such as, for example, a Hall effect sensor. A control module 60 is in communication with the first magnetic field sensors 50 and the second magnetic field sensors 52 through an interface 58.
The control module 60 controls the operation of the power steering system 10. Referring now to
c1=α−360 n1 (Equation 1)
c2=Gα−360 n2 (Equation 2)
α=c1+360 n1 (Equation 3)
where n1 is the number of rotations of the input shaft 22 (having a total of 5 rotations, within the range of 0 to 1799 degrees) and n2 is the number of rotations of the puck gear 30 (having a total of 11 rotations). Using equations 1-2 above, equation 4 may be derived as:
1/360[c1−1/G c2]=1/G n2−n1 (Equation 4)
where G is the gear ratio. For a given value of n1 and n2, there is a unique value for [c1−1/G c2]. The term [c1−1/G c2] is an empirical value that is used to determine the number of rotations of the input shaft n1. In one approach, a gear ratio of 1:2.2 may be used (e.g., thus equation 4 would be 1/360[c1−1/2.2 c2]=1/2.2 n2−n1). Turning now to
TABLE 1
Line C Level
n1
n2
0
0
0
163
0
1
327
0
2
−33
1
2
130
1
3
294
1
4
−66
2
4
98
2
5
261
2
6
−99
3
6
65
3
7
229
3
8
−131
4
8
32
4
9
196
4
10
Referring now to Table 1 and
Referring to FIGS. 1 and 3-4, the respective positions of the ring magnet 26 (Line A) and the puck gear 30 (Line B) should be generally aligned at zero degrees (at the hand wheel position) to accurately calculate the hand wheel position α. However, referring now to
If (c1−c1
new—c1=(c1−c1
Else if (c1−c1
new—c1=(c1−c1
Else
new_c1=c1
where c1 is the position of the ring magnet 26 indicated by Line A′, and c1
Referring to
α′=(c2+360 n2)/G (Equation 5)
The diagnostic module 66 then determines the error within the hand wheel position α by comparing the hand wheel position α using equation 3, and a second hand wheel position α′, and determining if the difference between the two values is above a threshold value. The error may be calculated by equation 6:
|α−α′|=Error (Equation 6)
The error in equation 6 may be set to any threshold value. In one exemplary embodiment, the error may be set to a threshold value of five degrees. Thus, if the term |α−α′| results in more than five degrees, this indicates the error has exceeded the threshold value.
Turning now to
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.
Kidder, Keith A., Sebastian, Tomy, Ross, Christian E., Ryne, Zaki, Tarum, Carl D., Fisher, Paul M., Blehm, Scott T.
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